feat: make webpack compilation hash value available to templates (#13)

* Make webpack compilation hash value available to templates

* feat: drop node 4 (#14)

* Drop node 4 support in travis ci

* Add node 10 and 11 in travis build matrix

* Update engines prop in package.json

* Use LTS version of node v6 as a minimum

Author: burt202

README.md

@@ -67,7 +67,10 @@ export default {
 
   * `context` - (optional) instead global `context` (see above), see
     [render](https://mozilla.github.io/nunjucks/api.html#render) second
-    argument.
+    argument. The following webpack compilation variables are also sent
+    through to the template under the `__webpack__` object:
+
+    * hash
 
   * `callback` - (optional) instead global `callback` (see above), see
     [render](https://mozilla.github.io/nunjucks/api.html#render) third argument.

src/NunjucksWebpackPlugin.js

@@ -52,6 +52,12 @@ class NunjucksWebpackPlugin {
 
       const promises = [];
 
+      const baseContext = {
+        __webpack__: {
+          hash: compilation.hash
+        }
+      };
+
       this.options.templates.forEach(template => {
         if (!template.from) {
           throw new Error("Each template should have `from` option");
@@ -67,7 +73,7 @@ class NunjucksWebpackPlugin {
 
         const res = configure.render(
           template.from,
-          template.context ? template.context : null,
+          Object.assign(baseContext, template.context),
           template.callback ? template.callback : null
         );
 

src/__tests__/NunjucksWebpackPlugin-test.js

@@ -144,3 +144,40 @@ test("should execute successfully when option `templates` is passed and `templat
     });
   });
 });
+
+test("should execute successfully when using props from '__webpack__' base context object", t => {
+  const tmpDirectory = tempy.directory();
+  const templateName = "test3.njk";
+  const webpackConfig = Object.assign({}, webpackConfigBase, {
+    output: {
+      filename: "bundle.js",
+      path: tmpDirectory
+    },
+    plugins: [
+      new NunjucksWebpackPlugin({
+        templates: [
+          {
+            from: path.join(fixturesDir, templateName),
+            to: path.join(tmpDirectory, path.basename(templateName, ".njk"))
+          }
+        ]
+      })
+    ]
+  });
+
+  return pify(webpack)(webpackConfig).then(stats => {
+    t.true(stats.compilation.errors.length === 0, "no compilation error");
+
+    return pify(fs.readFile)(
+      path.join(tmpDirectory, path.basename(templateName, ".njk"))
+    ).then(data => {
+      const contents = data.toString();
+
+      t.true(
+        contents.trim() === '<script src="029f359d6e9653eafd07.js"></script>'
+      );
+
+      return true;
+    });
+  });
+});

src/__tests__/fixtures/test3.njk

@@ -0,0 +1 @@
+<script src="{{__webpack__.hash}}.js"></script>